Method and apparatus for storing liquefied gases



Dec. 18, 1962 JOHNSTON METHOD AND APPARATUS FOR STORING LIQUEFIED GASES Original Filed May 4, 1959 INVENTOR. HERRICK L. JOHNSTON 2210 D24 JAE 22x0 024 J zu wOmDOw 2DDO w 0 QmNEDwwwmm m0 uumDow 4 mm rl lL mm .III 4 1050] omfimammwmm o momnow ATTORNEY.

United States Patent ()fifice 3,069,042 Patented Dec. 18, 1962 3,069,042 7 METHOD AND APPARATUS FOR STORING Ll'QUEFIED GASES Herrick L. Johnston, Columbus, Ohio, assiguor to The Herrick L. Johnston, Inc, Columbus, Ohio, a corporation of Ohio Continuation of abandoned application Ser. No. 810,796, May 4, 1959. This application July 6, 19 61, Ser. No. 122,332

2 Claims. (Cl. 220-) This is a continuation of United States patent application Serial No. 810,796, filed May 4, 1959, and now abandoned.

The present invention relates to storing volatile cryogenic liquids and particularly to a novel method and apparatus whereby the rate of boil off is substantially reduced. While the invention is of particular utility in the storage of helium it is not limited thereto.

The invention is based on my discovery that the rate of pressure rise of stored helium is greater when the liquid is quiescent than when it is agitated, as during transportation. In one demonstration I found that under typical service conditions the vapor pressure rise during transportation was only one-third of the comparable rise under static conditions, 5.5 pounds per square inch as compared to 16.8 pounds per square inch in twenty-four hours.

' The three times smaller rate of pressure increase during transport, as compared to static conditions, is contrary to the usual experience in the transport of cryogenic liquids, such as oxygen. In the usual case, transport is characterized by a greater rate of pressure rise, attributable to conversion of the kinetic energy of the splashing liquid into the thermal energy.

My experiments led to the conclusion that the high rate of pressure rise of quiescent liquid is due to the large volume coefficient of thermal expansion for liquid helium, which results in stratification of the liquid, the warm liquid being at the surface. The rate of boil off is a function of the temperature of this warm liquid. The prevention of this condition, in accordance with the invention, accomplishes the result of increasing the period of time during which the liquid can be stored without ventmg.

Accordingly, it is an object of the invention to provide a means and method for storing such cryogenic liquids as helium or the like, which are effective to prevent vertical stratification: i.e., the presence of warm liquid (of low density) on the evaporating surface, while the colder liquid remains at the bottom.

My experiments have further established that undesired vertical stratification is a stable condition, due to the fact that the liquid is per se not a good heat conductor. Accordingly, it is an object of the invention to provide an apparatus and method for eliminating such undesired stability and for preventing vertical Stratification by causing the distribution of heat throughout the body of the stored liquid or by preventing the occurrence of the conditions which cause stratification.

In accordance with the invention there is provided a container for the storage of cryogenic liquids, including conductors of high thermal conductivity for providing heat transfer paths between the upper and lower portions of the container. This means may take various forms. For example, in the preferred embodiment of the invention, the heat is distributed throughout the body of the liquid as by the introduction of aluminum or copper mesh screening through the liquid space. This mesh network in the preferred embodiment is illustrative of one mode of practicing the invention; such alternative structures as loosely crumbled wire mesh or vertically positioned heat conductive rods can be used and are within the teachings of the present invention.

For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following description of the appended drawings, in which:

FIG. 1 is a schematic view of a storage means with anti Stratification means in accordance with the invention, FIG. 1 being a sectional view taken on line 1-1 of FIG. 2;

FIG. 2 is a sectional view taken on line 2-2 of FIG. 1, again looking in the direction of the arrows;

FIG. 3 is a perspective View showing a detail of the Way in which the screen elements of the anti-stratification means articulate with each other; and

FIG. 4 is a perspective view of the anti-Stratification screening means per se.

In accordance with a particular embodiment of the invention, vertically extending screens 8 and 9, etc. are disposed lengthwise or axially of the container 40. Each of the elements 8 and 9 is a meshed screen made of electrolytic copper, for example, or aluminum, or a suitable metal having high heat conductivity at temperatures involved in cryogenic liquids. Similarly, the screens, 8, 9, etc. are generally of rectangular outline. Similarly, circular screens 5, 6, "I, etc. are vertically arranged parallel to the ends of the container. The screens 8, 9, etc. are spaced from each other and the screens 5, 6, 7, etc. are spaced from each other so that heat is distributed throughout the body of liquid disposed in that container, the screens providing a ready path for the transfer of heat between the upper and lower portions of the stored liquid, thus preventing the undesired vertical stratification discussed above.

The screen elements 7 and 8, for example, are notched as indicated at and 91, respectively, to provide for ,articulation or interdigitation.

The anti-stratification means in accordance with the invention is shown as incorporated in storage means of the type disclosed and claimed in my United States Patent No. 2,863,297, issued December 9, 1958, and assigned to the same assignee as the present application and invention. -This apparatus includes a storage means indicated generally at 10. Storage means 10 includes an outer jacket 12 which surrounds an insulating space 13. Insulating space may be in the form of a vacuum chamber or it may be formed as a vacuum chamber containing insulating material such as fine particles of low conductivity and high reflectivity. A vacuum can be maintained in the insulating space 13 by connecting such space with a source of vacuum 20 by means of the lines 16 and 17. A valve 18 is located along line 17 to control and maintain the vacuum in insulating space 13.

A radiation shield structure is indicated generally at 22. Radiation shield 22 is supported within the outer jacket 12 by a plurality of structural members 24, 25, 26 and 27, which extend between the inner wall of the outer jacket 12 and an outer wall 30 of the radiation shield. For example, structural member 24 has one end thereof secured to the outer jacket 12 at 28, and the other end thereof secured to the radiation shield 22 at 29.

Radiation shield 22 further includes an inner wall 32 and end walls 33 and 34 which form a sealed chamber 36. Chamber 36 of the radiation shield substantially surrounds a second insulating means indicated generally at 38 and provided with an outer shell 42. Insulating means 38 in turn surrounds a container 40 which directly contains the liquid being stored.

Referring further to the inner container 40, such container is supported in spaced relationship with the radiation shield 22 and wall means 42. by means of a plurality of structural members such as are exemplified by the 3 members indicated at 44, 45, 46 and 47. For example, structural member 44 has one end thereof secured to the inner side of wall 32 at 49, and the other end thereof secured to the outer side of wall 41 at 50.

Since the inner container 40 is supported by the radiation shield structure 22, and since the radiation shield structure is suspended within the outer shell 12 it will be understood that the inner container 40 is maintained in substantially rigid suspension relative to the surrounding structure of the storage means.

The inner container can be filled and drained of the liquid to be stored by means of a line 60 and valve 61. The inner container is further provided with a safety pressure release valve 63 which is connected to the inner container by means of a line 64.

Reference is again made to the radiation shield 22 and particularly to chamber 36 thereof which is adapted to receive and store a fluid in the liquid state. A fluid having a boiling point lower than the boiling point of the stored liquid, such as nitrogen, is utilized to provide a radiation shield which is maintained colder than the liquid being stored. A line 66 and valve 67 serve to fill and drain the colder liquid carried in chamber 36, and a safety pressure relief control valve 7 is connected with the chamber 36 by means of a line 71.

Reference is next made to the inner insulating means 38 which includes a chamber 75 in surrounding relationship with the inner container 40. Chamber 75 is connected to the source of vacuum 20 by means of a line 77 which extends from chamber 75 to the vacuum line 16. A valve 78 is interposed along the line so that the chamber 75 can be selectively isolated from the vacuum source 20. A pressurization source 80 is connected to chamber 75 by lines 81 and 77, and a valve 83 is provided for controlling the rate of gas fiow from the pressurization source 80, or for isolating such source from the chamber 75. To elfect control of the pressure of the radiation shield liquid, such as nitrogen, a variable pressurization means, schematically illustrated at 85, can be connected to the line 71 by means of a line 87 and a valve 88.

The invention is of particular utility when used in conjunction with large storage containers. The observations discussed above were made from measurements taken with a helium storage vessel of 750 liters capacity, with a liquid shield having a volume of 900 liters of nitrogen. While there has been shown and described what is at present considered to be the preferred embodiment of the invention, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the true scope of the invention, as defined in the appended claims.

I claim:

1. Apparatus for the storage of liquid helium comprising a double-walled insulated closed storage container and two groups of spaced vertically oriented thermally conductive bafile screens perforated throughout and extending from the bottom of the container toward the top to minimize density stratification, said groups of screens being formed to be interdigitally secured, one of said groups extending axially of the container and including a plurality of parallel screens, the other group extending transversely of the container and including a plurality of parallel screens.

2. Apparatus for the storage of liquid helium comprising a double walled insulated closed container and two groups of vertically oriented thermally conductive meshed screens extending from the bottom of the container to the top thereof to minimize density stratification throughout the stored helium, each of said groups of screens including a plurality of spaced parallel members, one of said groups extending axially of said container and the other of said groups extending transversely of said container.

References Cited in the file of this patent UNITED STATES PATENTS 

2. APPARATUS FOR THE STORAGE OF LIQUID HELIUM COMPRISING A DOUBLE WALLED INSULATED CLOSED CONTAINER AND TWO GROUPS OF VERTICALLY ORIENTED THERMALLY CONDUCTIVE MESHED SCREENS EXTENDING FROM THE BOTTOM OF THE CONTAINER TO THE TOP THEREOF TO MINIMIZE DENSITY STRATIFICATION THROUGHOUT 